[linux-audio-dev] Re: Which widgets?

[Jussi Laako]

On Sun, 2006-02-26 at 20:38 +0100, Albert Graef wrote:
> Canvases give you much more than just rendering. They also manage the 
> graphical objects that you created and, if anything changes, rerendering 
> the changed parts happens automatically.

That's usually bad and undesirable for any real time graphics rendering,
like audio UIs often are. For example with proper interfaces I can now
get full screen scrolling spectrogram at 50-100 fps without huge CPU
load.

> Moreover, they let you inspect 
> the object model of the rendered graphic. Does Cairo do that for you? 

Well, Gtk+ uses Cairo nowadays anyway... Coordinate transformations,
etc. make it reasonable to also get proper printer output.

> OpenGL can do something like this with its display lists, but that's a 
> very low-level abstraction compared to what canvas widgets offer.

Probably you could create proper canvas implementation on top of
Cairo/OpenGL, but most of the current implementations I've seen are dead
slow. I'm not sure if GnomeCanvas or some other implementation has been
converted to Cairo yet...


	- Jussi